In this demonstration, light is emitted from a bulb at the center of the train, but when the presidents receive the light signals, they don’t sign the treaty. Instead, each president immediately fires a laser pulse at the opposing president (represented as balls of light bouncing off the train walls). Notice that from the ground perspective, the President of Forwardland (on the left) receives the light signal first and hence fires first. Nevertheless, from the ground perspective, the President of Forwardland also gets hit by the laser fire before the President of Backwardland (on the right).